Claims
- 1. A machine having an operative structure configured to perform a task, where the operative structure includes a cutting tool, the machine comprising:
a detection subsystem adapted to detect contact between a person and a specified portion of the operative structure, and to distinguish that contact from contact between at least one other material and the specified portion of the operative structure, where the detection subsystem imparts an electrical signal to the specified portion, and where the detection subsystem distinguishes contact between the person and the specified portion from contact between the other material and the specified portion based on a predetermined frequency response of the electrical signal; and a reaction subsystem adapted to cause a predetermined action to take place upon detection of the contact between the person and the specified portion.
- 2. The machine of claim 1, where the other material is wood having a moisture content of at least a predetermined level.
- 3. The machine of claim 1, where the other material is metal.
- 4. The machine of claim 1, where the other material is a high-dielectric material.
- 5. The machine of claim 1, where the cutting tool is a blade, and where the detection subsystem imparts the electrical signal to the blade.
- 6. The machine of claim 1, where the predetermined frequency response corresponds to charging and/or discharging the person's body.
- 7. The machine of claim 1, where the electrical signal has a period comparable to the RC-time constant of a human body impedance.
- 8. The machine of claim 1, where the electrical signal varies over a range of frequencies.
- 9. The machine of claim 1, where the electrical signal includes multiple frequency components, and where the detection subsystem distinguishes contact between the person and the specified portion from contact between the other material and the specified portion based on frequency responses to multiple frequency components.
- 10. The machine of claim 1, where the electrical signal includes a pulse width of approximately one RC-time constant of the person's body impedance.
- 11. The machine of claim 1, where the electrical signal includes a pulse width greater than one RC-time constant of the person's body impedance.
- 12. The machine of claim 1, where the electrical signal includes a pulse width of at least two RC-time constants of the person's body impedance.
- 13. The machine of claim 1, where the electrical signal includes a pulse width less than one RC-time constant of the person's body impedance.
- 14. The machine of claim 1, where the electrical signal is configured with multiple frequencies, at least one frequency having periods greater than the RC-time constant of the person's body and at least one frequency having periods less than the RC-time constant of the person's body.
- 15. The machine of claim 1, where the electrical signal is configured with a single frequency comparable to the maximum frequency response of the specified portion of the operative structure when contacted by the person's body.
- 16. The machine of claim 1, where the detection subsystem is tuned to the frequency response of a particular person.
- 17. The machine of claim 1, where the operative structure is configured to perform the task of cutting wood.
- 18. A machine having an operative structure configured to perform a task, where the operative structure includes a cutting tool, the machine comprising:
detection means for detecting contact between a person and a specified portion of the operative structure, and for distinguishing that contact from contact between at least one other material and the specified portion of the operative structure based on a frequency response of an electrical signal; and a reaction subsystem adapted to cause a predetermined action to take place upon detection of the contact between the person and the specified portion.
- 19. A method of detecting contact between a human body and a specified portion of a machine, and of distinguishing that contact from contact between at least one other material and the machine, the method comprising:
imparting an electrical signal on the specified portion of the machine; measuring the frequency response of the electrical signal when the specified portion is in contact with the human body; measuring the frequency response of the electrical signal when the specified portion in contact with the other material; comparing the frequency response of the electrical signal when the specified portion is in contact with the human body to the frequency response of the electrical signal when the specified portion is in contact with the other material; and setting frequency measurement parameters to distinguish human body contact from contact by the other material.
- 20. The method of claim 19, where the machine is a power saw, where the specified portion is a blade, and where the method is employed to mitigate injury from contact between the human body and the blade.
CROSS-REFERENCE TO RELATED APPLICATION
[0001] This application claims the benefit of and priority from the following U.S. Provisional Patent Application, the disclosure of which is herein incorporated by reference: Serial No. 60/335,970, filed Nov. 13, 2001.
Provisional Applications (1)
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Number |
Date |
Country |
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60335970 |
Nov 2001 |
US |